directory rename detection: testcases to avoid taking detection too far

Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t6043-merge-rename-directories.sh

@@ -582,4 +582,157 @@ test_expect_success '2b-check: Directory split into two on one side, with equal
 #   messages are handled correctly.
 ###########################################################################
 
+
+###########################################################################
+# SECTION 3: Path in question is the source path for some rename already
+#
+# Combining cases from Section 1 and trying to handle them could lead to
+# directory renaming detection being over-applied.  So, this section
+# provides some good testcases to check that the implementation doesn't go
+# too far.
+###########################################################################
+
+# Testcase 3a, Avoid implicit rename if involved as source on other side
+#   (Related to testcases 1c and 1f)
+#   Commit O: z/{b,c,d}
+#   Commit A: z/{b,c,d} (no change)
+#   Commit B: y/{b,c}, x/d
+#   Expected: y/{b,c}, x/d
+test_expect_success '3a-setup: Avoid implicit rename if involved as source on other side' '
+	test_create_repo 3a &&
+	(
+		cd 3a &&
+
+		mkdir z &&
+		echo b >z/b &&
+		echo c >z/c &&
+		echo d >z/d &&
+		git add z &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		test_tick &&
+		git commit --allow-empty -m "A" &&
+
+		git checkout B &&
+		mkdir y &&
+		mkdir x &&
+		git mv z/b y/ &&
+		git mv z/c y/ &&
+		git mv z/d x/ &&
+		rmdir z &&
+		test_tick &&
+		git commit -m "B"
+	)
+'
+
+test_expect_success '3a-check: Avoid implicit rename if involved as source on other side' '
+	(
+		cd 3a &&
+
+		git checkout A^0 &&
+
+		git merge -s recursive B^0 &&
+
+		git ls-files -s >out &&
+		test_line_count = 3 out &&
+
+		git rev-parse >actual \
+			HEAD:y/b HEAD:y/c HEAD:x/d &&
+		git rev-parse >expect \
+			O:z/b    O:z/c    O:z/d &&
+		test_cmp expect actual
+	)
+'
+
+# Testcase 3b, Avoid implicit rename if involved as source on other side
+#   (Related to testcases 5c and 7c, also kind of 1e and 1f)
+#   Commit O: z/{b,c,d}
+#   Commit A: y/{b,c}, x/d
+#   Commit B: z/{b,c}, w/d
+#   Expected: y/{b,c}, CONFLICT:(z/d -> x/d vs. w/d)
+#   NOTE: We're particularly checking that since z/d is already involved as
+#         a source in a file rename on the same side of history, that we don't
+#         get it involved in directory rename detection.  If it were, we might
+#         end up with CONFLICT:(z/d -> y/d vs. x/d vs. w/d), i.e. a
+#         rename/rename/rename(1to3) conflict, which is just weird.
+test_expect_success '3b-setup: Avoid implicit rename if involved as source on current side' '
+	test_create_repo 3b &&
+	(
+		cd 3b &&
+
+		mkdir z &&
+		echo b >z/b &&
+		echo c >z/c &&
+		echo d >z/d &&
+		git add z &&
+		test_tick &&
+		git commit -m "O" &&
+
+		git branch O &&
+		git branch A &&
+		git branch B &&
+
+		git checkout A &&
+		mkdir y &&
+		mkdir x &&
+		git mv z/b y/ &&
+		git mv z/c y/ &&
+		git mv z/d x/ &&
+		rmdir z &&
+		test_tick &&
+		git commit -m "A" &&
+
+		git checkout B &&
+		mkdir w &&
+		git mv z/d w/ &&
+		test_tick &&
+		git commit -m "B"
+	)
+'
+
+test_expect_success '3b-check: Avoid implicit rename if involved as source on current side' '
+	(
+		cd 3b &&
+
+		git checkout A^0 &&
+
+		test_must_fail git merge -s recursive B^0 >out &&
+		test_i18ngrep CONFLICT.*rename/rename.*z/d.*x/d.*w/d out &&
+		test_i18ngrep ! CONFLICT.*rename/rename.*y/d out &&
+
+		git ls-files -s >out &&
+		test_line_count = 5 out &&
+		git ls-files -u >out &&
+		test_line_count = 3 out &&
+		git ls-files -o >out &&
+		test_line_count = 1 out &&
+
+		git rev-parse >actual \
+			:0:y/b :0:y/c :1:z/d :2:x/d :3:w/d &&
+		git rev-parse >expect \
+			 O:z/b  O:z/c  O:z/d  O:z/d  O:z/d &&
+		test_cmp expect actual &&
+
+		test_path_is_missing z/d &&
+		git hash-object >actual \
+			x/d   w/d &&
+		git rev-parse >expect \
+			O:z/d O:z/d &&
+		test_cmp expect actual
+	)
+'
+
+###########################################################################
+# Rules suggested by section 3:
+#
+#   Avoid directory-rename-detection for a path, if that path is the source
+#   of a rename on either side of a merge.
+###########################################################################
+
 test_done